Musical composition data creation device and method

ABSTRACT

An apparatus and a method for making music data each perform converting an input audio signal indicative of a music piece into a frequency signal indicative of magnitudes of frequency components at predetermined time intervals; extracting frequency components corresponding to tempered tones respectively at the predetermined time intervals from the frequency signal; detecting two chords each formed by a set of three frequency components as the first and second chord candidates, the three frequency components having a large total level of the frequency components corresponding to the extracted tones; and smoothing trains of the detected first and second chord candidates to produce music data.

TECHNICAL FIELD

The present invention relates to an apparatus and a method for makingdata indicative of a music piece.

BACKGROUND ART

In Japanese Patent Publication Kokai No. Hei 5-289672, an apparatus isdisclosed which recognizes chords of a music piece to make datarepresenting the music piece as variations in the chords, i.e., as chordprogression.

In accordance with music information previously notated (noteinformation of sheet music), the apparatus disclosed in the publicationdetermines a chord based on note components appearing at each beat orthose that are obtained by eliminating notes indicative of non-harmonicsound from the note components, thereby making data representative ofthe chord progression of the music piece.

However, in the conventional music date making apparatus, music pieceswith known beats of which chords can be analyzed are limited, and dataindicative of chord progression from music sound with unknown beats cannot be made.

Additionally, it is impossible for the conventional apparatus to analyzechords of a music piece from an audio signal indicative of the sound ofthe music piece in order to make data as chord progression.

DISCLOSURE OF INVENTION

The problems to be solved by the present invention include theaforementioned problem as one example. It is therefore an object of thepresent invention to provide an apparatus and a method for making musicdata, in which music chord progression are detected in accordance withan audio signal indicative of music sound to make data representative ofthe chord progression.

An apparatus for making music data according to the present invention,comprises: frequency conversion means for converting an input audiosignal indicative of a music piece into a frequency signal indicative ofmagnitudes of frequency components at predetermined time intervals;component extraction means for extracting frequency componentscorresponding to tempered tones respectively at the predetermined timeintervals from the frequency signal obtained by the frequency conversionmeans; chord candidate detecting means for detecting two chords eachformed by a set of three frequency components as the first and secondchord candidates, the three frequency components having a large totallevel of the frequency components corresponding to the tones extractedby the component extracting means; and smoothing means for smoothingtrains of the first and second chord candidates repeatedly detected bythe chord candidate detecting means to produce music data.

A method for making music data according to the present invention,comprises the steps of: converting an input audio signal indicative of amusic piece into a frequency signal indicative of magnitudes offrequency components at predetermined time intervals; extractingfrequency components corresponding to tempered tones respectively at thepredetermined time intervals from the frequency signal; detecting twochords each formed by a set of three frequency components as the firstand second chord candidates, the three frequency components having alarge total level of the frequency components corresponding to theextracted tones; and smoothing trains of the respective detected firstand second chord candidates to produce music data.

A computer-readable program according to the present invention, which isadapted to execute a method for making music data in accordance with aninput audio signal indicative of a music piece, comprises: a frequencyconversion step for converting the input audio signal into a frequencysignal indicative of magnitudes of frequency components at predeterminedtime intervals; a component extraction step for extracting frequencycomponents corresponding to tempered tones respectively at thepredetermined time intervals from the frequency signal obtained in thefrequency conversion step; a chord candidate detecting step fordetecting two chords each formed by a set of three frequency componentsas the first and second chord candidates, the three frequency componentshaving a large total level of the frequency components corresponding tothe tones extracted in the component extracting step; and a smoothingstep for smoothing trains of the first and second chord candidatesrepeatedly detected in the chord candidate detecting step to producemusic data.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of the configuration of a music processingsystem to which the invention is applied;

FIG. 2 is a flow chart showing the operation of frequency errordetection;

FIG. 3 is a table of ratios of the frequencies of twelve tones and toneA one octave higher with reference to the lower tone A as 1.0;

FIG. 4 is a flow chart showing a main process in chord analysisoperation;

FIG. 5 is a graph showing one example of the intensity levels of tonecomponents in band data;

FIG. 6 is a graph showing another example of the intensity levels oftone components in band data;

FIG. 7 shows how a chord with four tones is transformed into a chordwith three tones;

FIG. 8 shows a recording format into a temporary memory;

FIGS. 9A to 9C show method for expressing fundamental notes of chords,their attributes, and a chord candidate;

FIG. 10 is a flow chart showing a post-process in chord analysisoperation;

FIG. 11 shows chronological changes in first and second chord candidatesbefore a smoothing process;

FIG. 12 shows chronological changes in first and second chord candidatesafter the smoothing process;

FIG. 13 shows chronological changes in first and second chord candidatesafter an exchanging process;

FIGS. 14A to 14D show how chord progression music data is produced andits format;

FIG. 15 is a block diagram of the configuration of a music processingsystem as another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings.

FIG. 1 shows a music processing system to which the present invention isapplied. The music processing system includes a microphone input device1, a line input device 2, a music input device 3, an input operationdevice 4, an input selector switch 5, an analog-digital converter 6, achord analysis device 7, data storing devices 8 and 9, a temporarymemory 10, a chord progression comparison device 11, a display device12, a music reproducing device 13, a digital-analog converter 14, and aspeaker 15.

The microphone input device 1 can collect a music sound with amicrophone and outputs an analog audio signal representing the collectedmusic sound. The line input device 2 is connected, for example, with adisc player or a tape recorder, so that an analog audio signalrepresenting a music sound can be input. The music input device 3 is,for example, a CD player connected with the chord analysis device 7 andthe data storing device 8 to reproduce a digitized audio signal (such asPCM data). The input operation device 4 is a device for a user tooperate for inputting data or commands to the system. The output of theinput operation device 4 is connected with the input selector switch 5,the chord analysis device 7, the chord progression comparison device 11,and the music reproducing device 13.

The input selector switch 5 selectively supplies one of the outputsignals from the microphone input device 1 and the line input device 2to the analog-digital converter 6. The input selector switch 5 operatesin response to a command from the input operation device 4.

The analog-digital converter 6 is connected with the chord analysisdevice 7 and the data storing device 8, digitizes an analog audiosignal, and supplies the digitized audio signal to the data storingdevice 8 as music data. The data storing device 8 stores the music data(PCM data) supplied from the analog-digital converter 6 and the musicinput device 3 as files.

The chord analysis device 7 analyzes chords in accordance with thesupplied music data by executing a chord analysis operation that will bedescribed. The chords of the music data analyzed by the chord analysisdevice 7 are temporarily stored as first and second chord candidates inthe temporary memory 10. The data storing device 9 stores chordprogression music data (first chord progression music data), which isanalyzed result by the chord analysis device 7, as a file for each musicpiece.

The chord progression comparison device 11 compares the chordprogression music data (second chord progression music data) as anobject of search and the chord progression music data stored in the datastoring device 9, and chord progression music data with highsimilarities to the chord progression music data of the search object isdetected. The display device 12 displays a result of the comparison bythe chord progression comparison device 11 as a list of music pieces.

The music reproducing device 13 reads out the data file of the musicpiece detected as showing the highest similarity by the chordprogression comparison device 11 from the data storing device 8,reproduces the data, and outputs as a digital audio signal. Thedigital-analog converter 14 converts the digital audio signal reproducedby the music reproducing device 13 into an analog audio signal.

The chord analysis device 7, the chord progression comparison device 11,and the music reproducing device 13 each operate in response to acommand from the input operation device 4.

The operation of the music processing system will be described in detailbelow.

Here, assuming that an analog audio signal representing a music sound issupplied from the line input device 2 to the analog-digital converter 6through the input selector switch 5, and then converted into a digitalsignal for supply to the chord analysis device 7, the operation isdescribed.

The chord analysis operation includes a pre-process, a main process, anda post-process. The chord analysis device 7 carries out frequency errordetection operation as the pre-process.

In the frequency error detection operation, as shown in FIG. 2, a timevariable T and a band data F(N) each are initialized to zero, and avariable N is initialized, for example, to the range from −3 to 3 (stepS1). An input digital signal is subjected to frequency conversion byFourier transform at intervals of 0.2 seconds, and as a result of thefrequency conversion, frequency information f(T) is obtained (step S2).

The present information f(T), previous information f(T−1), andinformation f(T−2) obtained two times before are used to carry out amoving average process (step S3). In the moving average process,frequency information obtained in two operations in the past are used onthe assumption that a chord hardly changes within 0.6 seconds. Themoving average process is carried out by the following expression:f(T)=(f(T)+f(T−1)/2.0+f(T−2)/3.0)/3.0  (1)

After step S3, the variable N is set to −3 (step S4), and it isdetermined whether or not the variable N is smaller than 4 (step S5). IfN<4, frequency components f1(T) to f5(T) are extracted from thefrequency information f(T) after the moving average process (steps S6 toS10). The frequency components f1(T) to f5(T) are in tempered twelvetone scales for five octaves based on 110.0+2×N Hz as the fundamentalfrequency. The twelve tones are A, A#, B, C, C#, D, D#, E, F, F#, G, andG#. FIG. 3 shows frequency ratios of the twelve tones and tone A oneoctave higher with reference to the lower tone A as 1.0. Tone A is at110.0+2×N Hz for f1(T) in step S6, at 2×(110.0+2×N) Hz for f2(T) in stepS7, at 4×(110.0+2×N) Hz for f3(T) in step S8, at 8×(110.0+2×N) Hz forf4(T) in step S9, and at 16×(110.0+2×N) Hz for f5(T) in step 10.

After steps S6 to S10, the frequency components f1(T) to f5(T) areconverted into band data F′(T) for one octave (step S11). The band dataF′(T) is expressed as follows:F′(T)=f1(T)×5+f2(T)×4+f3(T)×3+f4(T)×2+f5(T)  (2)

More specifically, the frequency components f1(T) to f5(T) arerespectively weighted and then added to each other. The band data F′(T)for one octave is added to the band data F(N) (step S12). Then, one isadded to the variable N (step S13), and step S5 is again carried out.

The operations in steps S6 to S13 are repeated as long as N<4 stands instep S5, in other words, as long as N is in the range from −3 to +3.Consequently, the tone component F(N) is a frequency component for oneoctave including tone interval errors in the range from −3 to +3.

If N≧4 in step S5, it is determined whether or not the variable T issmaller than a predetermined value M (step S14). If T<M, one is added tothe variable T (step S15), and step S2 is again carried out. Band dataF(N) for each variable N for frequency information f(T) by M frequencyconversion operations is produced.

If T≧M in step S14, in the band data F(N) for one octave for eachvariable N, F(N) having the frequency components whose total is maximumis detected, and N in the detected F(N) is set as an error value X (stepS16).

In the case of existing a certain difference between the tone intervalsof an entire music sound such as a performance sound by an orchestra,the tone intervals can be compensated by obtaining the error value X bythe pre-process, and the following main process for analyzing chords canbe carried out accordingly.

Once the operation of detecting frequency errors in the pre-processends, the main process for analyzing chords is carried out. Note that ifthe error value X is available in advance or the error is insignificantenough to be ignored, the pre-process can be omitted. In the mainprocess, chord analysis is carried out from start to finish for a musicpiece, and therefore an input digital signal is supplied to the chordanalysis device 7 from the starting part of the music piece.

As shown in FIG. 4, in the main process, frequency conversion by Fouriertransform is carried out to the input digital signal at intervals of 0.2seconds, and frequency information f(T) is obtained (step S21). Thisstep S21 corresponds to a frequency converter. The present informationf(T), the previous information f(T−1), and the information f(T−2)obtained two times before are used to carry out moving average process(step S22). The steps S21 and S22 are carried out in the same manner assteps S2 and S3 as described above.

After step S22, frequency components f1(T) to f5(T) are extracted fromfrequency information f(T) after the moving average process (steps S23to S27). Similarly to the above described steps S6 to S10, the frequencycomponents f1(T) to f5(T) are in the tempered twelve tone scales forfive octaves based on 110.0+2×N Hz as the fundamental frequency. Thetwelve tones are A, A#, B, C, C#, D, D#, E, F, F#, G, and G#. Tone A isat 110.0+2×N Hz for f1(T) in step S23, at 2×(110.0+2×N) Hz for f2(T) instep S24, at 4×(110.0+2×N) Hz for f3(T) in step S25, at 8×(110.0+2×N) Hzfor f4(T) in step S26, and at 16×(110.0+2×N) Hz for f5(T) in step 27.Here, N is X set in step S16.

After steps S23 to S27, the frequency components f1(T) to f5(T) areconverted into band data F′(T) for one octave (step S28). The operationin step S28 is carried out using the expression (2) in the same manneras step S11 described above. The band data F′(T) includes tonecomponents. These steps S23 to S28 correspond to a component extractor.

After step S28, the six tones having the largest intensity levels amongthe tone components in the band data F′(T) are selected as candidates(step S29), and two chords M1 and M2 of the six candidates are produced(step S30). One of the six candidate tones is used as a root to producea chord with three tones. More specifically, ₆C₃ chords are considered.The levels of three tones forming each chord are added. The chord whoseaddition result value is the largest is set as the first chord candidateM1, and the chord having the second largest addition result is set asthe second chord candidate M2.

When the tone components of the band data F′(T) show the intensitylevels for twelve tones as shown in FIG. 5, six tones, A, E, C, G, B,and D are selected in step S29. Triads each having three tones fromthese six tones A, E, C, G, B, and D are chord Am (of tones A, C, andE), chord C (of tones C, E, and G), chord Em (of tones E, B, and G),chord G (of tones G, B, and D), . . . The total intensity levels ofchord Am (A, C, E), chord C (C, E, G), chord Em (E, B, G), and chord G(G, B, D) are 12, 9, 7, and 4, respectively. Consequently, in step S30,chord Am whose total intensity level is the largest, i.e., 12 is set asthe first chord candidate M1. Chord C whose total intensity level is thesecond largest, i.e., 7 is set as the second chord candidate M2.

When the tone components in the band data F′(T) show the intensitylevels for the twelve tones as shown in FIG. 6, six tones C, G, A, E, B,and D are selected in step S29. Triads produced from three tonesselected from these six tones C, G, A, E, B, and D are chord C (of tonesC, E, and G), chord Am (of A, C, and E), chord Em (of E, B, and G),chord G (of G, B, and D), . . . . The total intensity levels of chord C(C, E, G), chord Am (A, C, E), chord Em (E, B, G), and chord G (G, B, D)are 11, 10, 7, and 6, respectively. Consequently, chord C whose totalintensity level is the largest, i.e., 11 in step S30 is set as the firstchord candidate M1. Chord Am whose total intensity level is the secondlargest, i.e., 10 is set as the second chord candidate M2.

The number of tones forming a chord does not have to be three, and thereis, for example, a chord with four tones such as 7th and diminished 7th.Chords with four tones are divided into two or more chords each havingthree tones as shown in FIG. 7. Therefore, similarly to the above chordsof three tones, two chord candidates can be set for these chords of fourtones in accordance with the intensity levels of the tone components inthe band data F′(T).

After step S30, it is determined whether or not there are chords as manyas the number set in step S30 (step S31). If the difference in theintensity level is not large enough to select at least three tones instep 30, no chord candidate is set. This is why step S31 is carried out.If the number of chord candidates >0, it is then determined whether thenumber of chord candidates is greater than one (step S32).

If it is determined in step S31 that the number of chord candidates=0,the chord candidates M1 and M2 set in the previous main process at T−1(about 0.2 seconds before) are set as the present chord candidates M1and M2 (step S33). If the number of chord candidates=1 in step S32, itmeans that only the first candidate M1 has been set in the present stepS30, and. therefore the second chord candidate M2 is set as the samechord as the first chord candidate M1 (step S34). These steps S29 to S34correspond to a chord candidate detector.

If it is determined that the number of chord candidates>1 in step S32,it means that both the first and second chord candidates M1 and M2 areset in the present step S30, and therefore, time, and the first andsecond chord candidates M1 and M2 are stored in the temporary memory 10(step S35). The time and first and second chord candidates M1 and M2 arestored as a set in the temporary memory 10 as shown in FIG. 8. The timeis the number of how many times the main process is carried out andrepresented by T incremented for each 0.2 seconds. The first and secondchord candidates M1 and M2 are stored in the order of T.

More specifically, a combination of a fundamental tone (root) and itsattribute is used in order to store each chord candidate on a 1-bytebasis in the temporary memory 10 as shown in FIG. 8. The fundamentaltone indicates one of the tempered twelve tones, and the attributeindicates a type of chord such as major {4, 3}, minor {3, 4}, 7thcandidate {4, 6}, and diminished 7th (dim7) candidate {3, 3}. Thenumbers in the braces { } represent the difference among three toneswhen a semitone is 1. A typical candidate for 7th is {4, 3, 3}, and atypical diminished 7th (dim7) candidate is {3, 3, 3}, but the aboveexpression is employed in order to express them with three tones.

As shown in FIG. 9A, the 12 fundamental tones are each expressed on a16-bit basis (in hexadecimal notation). As shown in FIG. 9B, eachattribute, which indicates a chord type, is represented on a 16-bitbasis (in hexadecimal notation). The lower order four bits of afundamental tone and the lower order four bits of its attribute arecombined in that order, and used as a chord candidate in the form ofeight bits (one byte) as shown in FIG. 9C.

Step S35 is also carried out immediately after step S33 or S34 iscarried out.

After step S35 is carried out, it is determined whether the music hasended (step S36). If, for example, there is no longer an input analogaudio signal, or if there is an input operation indicating the end ofthe music from the input operation device 4, it is determined that themusic has ended. The main process ends accordingly.

Until the end of the music is determined, one is added to the variable T(step S37), and step S21 is carried out again. Step S21 is carried outat intervals of 0.2 seconds, in other words, the process is carried outagain after 0.2 seconds from the previous execution of the process.

In the post-process, as shown in FIG. 10, all the first and second chordcandidates M1(0) to M1(R) and M2(0) to M2(R) are read out from thetemporary memory 10 (step S41). Zero represents the starting point andthe first and second chord candidates at the starting point are M1(0)and M2(0). The letter R represents the ending point and the first andsecond chord candidates at the ending point are M1(R) and M2(R). Thesefirst chord candidates M1(0) to M1(R) and the second chord candidatesM2(0) to M2(R) thus read out are subjected to smoothing (step S42). Thesmoothing is carried out to cancel errors caused by noise included inthe chord candidates when the candidates are detected at the intervalsof 0.2 seconds regardless of transition points of the chords. As aspecific method of smoothing, it is determined whether or not a relationrepresented by M1(t−1)≠M1(t) and M1(t)≠M1(t+1) stand for threeconsecutive first chord candidates M1(t−1), M1(t) and M1(t+1). If therelation is established, M1(t) is equalized to M1(t+1). Thedetermination process is carried out for each of the first chordcandidates. Smoothing is carried out to the second chord candidates inthe same manner. Note that rather than equalizing M1(t) to M1(t+1),M1(t+1) may be equalized to M1(t).

After the smoothing, the first and second chord candidates are exchanged(step S43). There is little possibility that a chord changes in a periodas short as 0.6 seconds. However, the frequency characteristic of thesignal input stage and noise at the time of signal input can cause thefrequency of each tone component in the band data F′(T) to fluctuate, sothat the first and second chord candidates can be exchanged within 0.6seconds. Step S43 is carried out as a remedy for the possibility. As aspecific method of exchanging the first and second chord candidates, thefollowing determination is carried out for five consecutive first chordcandidates M1(t−2), M1(t−1), M1(t), M1(t+1), and M1(t+2) and five secondconsecutive chord candidates M2(t−2), M2(t−1), M2(t), M2(t+1), andM2(t+2) corresponding to the first candidates. More specifically, it isdetermined whether a relation represented by M1(t−2)=M1(t+2),M2(t−2)=M2(t+2), M1(t−1)=M1(t)=M1(t+1)=M2(t−2), andM2(t−1)=M2(t)=M2(t+1)=M1(t−2) is established. If the relation isestablished, M1(t−1)=M1(t)=M1(t+1)=M1(t−2) andM2(t−1)=M2(t)=M2(t+1)=M2(t−2) are determined, and the chords areexchanged between M1(t−2) and M2(t−2). Note that chords may be exchangedbetween M1(t+2) and M2(t+2) instead of between M1(t−2) and M2(t−2). Itis also determined whether or not a relation represented byM1(t−2)=M1(t+1), M2(t−2)=M2(t+1), M1(t−1)=M(t)=M1(t+1)=M2(t−2) andM2(t−1)=M2(t)=M2(t+1)=M1(t−2) is established. If the relation isestablished, M1(t−1)=M(t)=M1(t−2) and M2(t−1)=M2(t)=M2(t−2) aredetermined, and the chords are exchanged between M1(t−2) and M2(t−2).The chords may be exchanged between M1(t+1) and M2(t+1) instead ofbetween M1(t−2) and M2(t−2).

The first chord candidates M1(0) to M1(R) and the second chordcandidates M2(0) to M2(R) read out in step S41, for example, change withtime as shown in FIG. 11, the averaging in step S42 is carried out toobtain a corrected result as shown in FIG. 12. In addition, the chordexchange in step S43 corrects the fluctuations of the first and secondchord candidates as shown in FIG. 13. Note that FIGS. 11 to 13 showchanges in the chords by a line graph in which positions on the verticalline correspond to the kinds of chords.

The candidate M1(t) at a chord transition point t of the first chordcandidates M1(0) to M1(R) and M2(t) at the chord transition point t ofthe second chord candidates M2(0) to M2(R) after the chord exchange instep S43 are detected (step S44), and the detection point t (4 bytes)and the chord (4 bytes) are stored for each of the first and secondchord candidates in the data storing device 9 (step S45). Data for onemusic piece stored in step S45 is chord progression music data. Thesesteps S41 to S45 correspond to a smoothing device.

When the first and second chord candidates M1(0) to M1(R) and M2(0) toM2(R), after exchanging the chords in step S43, fluctuate with time asshown in FIG. 14A, the time and chords at transition points areextracted as data. FIG. 14B shows the content of data at transitionpoints among the first chord candidates F, G, D, Bb (B flat), and F thatare expressed as hexadecimal data 0×08, 0×0A, 0×05, 0×01, and 0×08. Thetransition points t are T1(0), T1(1), T1(2), T1(3), and T1(4). FIG. 14Cshows data contents at transition points among the second chordcandidates C, Bb, F#m, Bb, and C that are expressed as hexadecimal data0×03, 0×01, 0×29, 0×01, and 0×03. The transition points t are T2(0),T2(1), T2(2), T2(3), and T2(4). The data contents shown in FIGS. 14B and14C are stored together with the identification information of the musicpiece in the data storing device 9 in step S45 as a file in the form asshown in FIG. 14D.

The chord analysis operation as described above is repeated foranalog-audio signals representing different music sounds. In this way,chord progression music data is stored in the data storing device 9 as afile for each of the plurality of music pieces. The above describedchord analysis operation is carried out for a digital audio signalrepresenting music sound supplied from the music input device 3, andchord progression music data is stored in the data storing device 9.Note that music data of PCM signals corresponding to the chordprogression music data in the data storing device 9 is stored in thedata storing device 8.

In step S44, a first chord candidate at a chord transition point of thefirst chord candidates and a second chord candidate at a chordtransition point of the second chord candidates are detected. Then, thedetected candidates form final chord progression music data, thereforethe capacity per music piece can be reduced even as compared tocompression data such as MP3, and data for each music piece can beprocessed at high speed.

The chord progression music data written in the data storing device 9 ischord data temporally in synchronization with the actual music.Therefore, when the chords are actually reproduced by the musicreproducing device 13 using only the first chord candidate or thelogical sum output of the first and second chord candidates, theaccompaniment can be played to the music.

FIG. 15 shows another embodiment of the invention. In the musicprocessing system in FIG. 15, the chord analysis device 7, the temporarymemory 10, and the chord progression comparison device 11 in the systemin FIG. 1 are formed by a computer 21. The computer 21 carries out theabove-described chord analysis operation and music searching operationaccording to programs stored in the storage device 22. The storagedevice 22 does not have to be a hard disk drive and may be a drive for astorage medium. In the case, chord progression music data may be writtenin the storage medium.

As described above, the present invention includes frequency conversionmeans, component extraction means, chord candidate detection means, andsmoothing means. Therefore, the chord progression of a music piece canbe detected in accordance with an audio signal representing the sound ofthe music piece, and as a result, data characterized by the chordprogression can be easily obtained.

1. An apparatus for making music data comprising: frequency conversionmeans for converting an input audio signal indicative of a music pieceinto a frequency signal indicative of magnitudes of frequency componentsat predetermined time intervals; component extraction means forextracting frequency components corresponding to tempered tonesrespectively at the predetermined time intervals from the frequencysignal obtained by said frequency conversion means; chord candidatedetecting means for detecting two chords each formed by a set of threefrequency components as said first and second chord candidates, saidthree frequency components having the largest total level of thefrequency components corresponding to the tones extracted by saidcomponent extracting means; and smoothing means for smoothing trains ofsaid first and second chord candidates repeatedly detected by said chordcandidate detecting means to produce music data.
 2. The apparatus formaking music data according to claim 1, wherein said frequencyconversion means performs a moving average process on the frequencysignal for output.
 3. The apparatus for making music data according toclaim 1, wherein said component extraction means comprises: filter meansfor extracting each frequency component corresponding to each of thetempered tones of a plurality of octaves; and means for individuallyweighting and adding together levels of frequency components eachcorresponding to each of the tempered tones of each octave output fromsaid filter means to output the frequency components corresponding tothe respective tempered tones of one octave.
 4. The apparatus for makingmusic data according to claim 1, further comprising frequency errordetection means for detecting a frequency error in a frequency componentcorresponding to each of the tempered tones of the input audio signal,wherein said component extraction means adds the frequency error to afrequency of each of the tempered tones for compensation, and extracts afrequency component after having been compensated.
 5. The apparatus formaking music data according to claim 4, said frequency error detectionmeans includes: second frequency conversion means for converting theinput audio signal at predetermined time intervals into a frequencysignal indicative of magnitudes of frequency components; means fordesignating one of a plurality of frequency errors each time said secondfrequency conversion means performs the frequency conversion by apredetermined number of times; filter means for extracting eachfrequency component having a frequency corresponding to each of thetempered tones of a plurality of octaves and the one frequency error;means for individually weighting and adding together levels of frequencycomponents corresponding to each of the tempered tones of each octaveoutput from said filter means to output a frequency componentcorresponding to each of the tempered tones of one octave; and addingmeans for calculating a sum of levels of each frequency components ofthe one octave for each of the plurality of frequency errors, wherein afrequency error having a maximum level provided by said adding means isemployed as a detected frequency error.
 6. The apparatus for makingmusic data according to claim 1, wherein said chord candidate detectionmeans defines a chord formed by a set of three frequency componentshaving a maximum value of the total level as the first chord candidate,and a chord formed by a set of three frequency components having asecond maximum value of the total level as the second chord candidate.7. The apparatus for making music data according to claim 1, whereinsaid smoothing means modifies contents of the first chord candidate orthe second chord candidate such that a predetermined number ofconsecutive first chord candidates in the train of the first chordcandidates are equal to each other and the predetermined number ofconsecutive second chord candidates in the train of the second chordcandidates are equal to each other.
 8. The apparatus for making musicdata according to claim 1, wherein said smoothing means provides only achord candidate at a time point of chord change in each train of thefirst and second chord candidates.
 9. The apparatus for making musicdata according to claim 1, wherein said smoothing means includes erroreliminating means, when of three consecutive first chord candidates inthe train of the first chord candidates, the beginning first chordcandidate is not equal to the middle first chord candidate and themiddle first chord candidate is not equal to the ending first chordcandidate, for making the middle first chord candidate equal to thebeginning first chord candidate or the ending first chord candidate, andwhen of three consecutive second chord candidates in the train of thesecond chord candidates, the beginning second chord candidate is notequal to the middle second chord candidate and the middle second chordcandidate is not equal to the ending second chord candidate, for makingthe middle second chord candidate equal to the beginning second chordcandidate or the ending second chord candidate, and transposing means,when of five consecutive first chord candidates in the train of thefirst chord candidates and of five consecutive second chord candidatesin the train of the second chord candidates, the first of the firstchord candidates is equal to the fifth of the first chord candidates;the first of the second chord candidates is equal to the fifth of thesecond chord candidates; the second, the third, and the fourth of thefirst chord candidates and the fifth of the second chord candidates areequal to each other; and the second, the third, and the fourth of thesecond chord candidates and the fifth of the first chord candidates areequal to each other, for making the first of first chord candidates orthe fifth of the first chord candidates equal to the second or thefourth of the first chord candidates and for making the first of secondchord candidates or the fifth of the second chord candidates equal tothe second through the fourth of the second chord candidates; and whenof the first to the fourth of the consecutive first chord candidates inthe train of the first chord candidates and of the first to the fourthof the consecutive second chord candidates in the train of the secondchord candidates, the first of the first chord candidates is equal tothe fourth of the first chord candidates; the first of the second chordcandidates is equal to the fourth of the second chord candidates; thesecond of the first chord candidates, the third of the first chordcandidates and the first of the second chord candidates are equal toeach other; and the second of the second chord candidates, the third ofthe second chord candidates and the first of the first chord candidatesare equal to each other, for making the first of the first chordcandidates or the fourth of the first chord candidates equal to thesecond and the third of the first chord candidates and making the firstof the second chord candidates or the fourth of the second chordcandidates equal to the second and the third of the second chordcandidates.
 10. The apparatus for making music data according to claim1, wherein the music data is indicative of a chord and a time point ofchord change in each train of the first and second chord candidates. 11.A method for making music data comprising the steps of: converting aninput audio signal indicative of a music piece into a frequency signalindicative of magnitudes of frequency components at predetermined timeintervals; extracting frequency components corresponding to temperedtones respectively at the predetermined time intervals from thefrequency signal; detecting two chords each formed by a set of threefrequency components as said first and second chord candidates, saidthree frequency components having the largest total level of thefrequency components corresponding to the extracted tones; and smoothingtrains of the respective detected first and second chord candidates toproduce music data.
 12. A program, stored on a computer-readable medium,adapted to execute a method for making music data in accordance with aninput audio signal indicative of a music piece, the program comprising:a frequency conversion step for converting the input audio signal into afrequency signal indicative of magnitudes of frequency components atpredetermined time intervals; a component extraction step for extractingfrequency components corresponding to tempered tones respectively at thepredetermined time intervals from the frequency signal obtained in saidfrequency conversion step; a chord candidate detecting step fordetecting two chords each formed by a set of three frequency componentsas said first and second chord candidates, said three frequencycomponents having the largest total level of the frequency componentscorresponding to the tones extracted in said component extracting step;and a smoothing step for smoothing trains of said first and second chordcandidates repeatedly detected in said chord candidate detecting step toproduce music data.